This invention relates to a double acting synchronizer.
Synchronizers for use in multi-ratio transmissions are well known. Such synchronizers include pairs of friction and jaw members for respectively synchronizing and positive clutching axially spaced apart ratio gears to a shaft, a hub rotatably fixed to the shaft and having external spline teeth slidably receiving internal spline teeth of a shift sleeve, blocker surfaces for arresting engaging movement of the shift sleeve until synchronization is reached and for transferring a shift force from the shift sleeve to axially movable friction rings. Such synchronizers often include pre-energizer assemblies for effecting initial engagement the friction members in response to initial engaging movement of shift sleeve. It is also known that the shift time and/or shift effort required by a vehicle operator, i.e., force applied to a shift lever, may be reduced by use of a synchronizer of the self-energizing type. A synchronizer of the self-energizing type may be seen by reference to U.S. Pat. No. 5,544,727, which is incorporated herein by reference.
The synchronizer in U.S. Pat. No. 5,544,727 has blocker surfaces that move axially with the shift sleeve and into engagement with blocker surfaces formed with the axially movable friction rings. Manufacturing complexity and cost of such friction rings may be reduced by forming the blocker surfaces on separate blocker members that attach to the friction rings.
Further, when double acting synchronizers are shifted from an engaged position with one ratio gear to the other ratio gear, the friction clutch of the ratio gear being disengaged may remain engaged enough to continue to transmit torque after the engagement of the friction clutch of the gear being engaged, thereby tending to rotate the friction rings relative to each other with damaging forces. The separate blocker members herein may include features for ensuring timely disengagement of the friction clutch to be disengaged.
An object of this invention is to provide a synchronizer with improved blockers.
According to the invention, a double acting synchronizer selectively synchronizes and positively connects a shaft with either of axially spaced apart first and second drives disposed for relative rotation about an axis of the shaft and axially fixed relative thereto. The synchronizer comprises: A hub is affixed to the shaft concentric to the axis and disposed between the first and second drives. First and second jaw teeth are respectively affixed to the first and second drives. First and second friction surfaces are rotatably fixed respectively to the first and second drives. A shift sleeve is mounted for fixed rotation with and axial movement relative to the hub and has third and fourth jaw teeth that are respectively engagable with the first and second jaw teeth in response to a to-or-fro axial engaging movement of the shift sleeve from a neutral position by a shift force. First and second friction rings are respectively associated with the first and second drives and respectively have third and fourth friction surfaces that are respectively movable axially into engagement with the first and second friction surfaces for producing a synchronizing torque. A plurality of first blocker surfaces are engagable with a plurality of second blocker surfaces in response to the to-or-fro movement of the shift sleeve for preventing asynchronous engagement of the engagable jaw teeth and for transmitting the operator shift force across the engaged blocker surfaces to effect synchronizing engagement of the friction surfaces. The first blocker surfaces are defined by first member means extending radially inward from the shift sleeve and affixed for axial movement thereto. And an axially extending second member means defines the second blocker surfaces and has first and second ends respectively having first and second portions for transmitting the operator shift force to the first and second friction rings.